This happens to fix another issue I ran into where boto was being
required when trying to start up the compute manager. This is because
virt/connection.py would import virt/libvirt/connection.py which would
import nova.auth.manager which would import nova.auth.signer which would
try to import boto.
Fortunately, we don't need to import nova.auth.manager in
libvirt/connection.py as it's no longer required.
Change-Id: I85f8e874ef3dc6f53667918ae081512115608d83